Help needed for SWFUpload module

I am trying to add the SWFUpload module to my CMS forms. However, as long as I added a line "$fields->addFieldToTab("Root.Content.File", new SWFUploadFileIFrameField('BigFile','Upload a file'), 'Photo');" (as stated on the documentation page), I get an empty admin page. By empty, I mean there is nothing on the page at all.